Electrospray sources are used in a variety of applications. U.S. Pat. No. 6,996,972 (incorporated herein by this reference), for example, discloses an electromagnetic spacecraft thruster with two showerheads each producing multiple jets. Each showerhead includes hundreds of micro-nozzles. Each micro-nozzle includes a conductive metallic layer coated with a thin insulative layer to form a frustum-shaped or conic truncated apex tip outlet resulting in a jet-producing Taylor cone of propellant. The inner diameter of each micro-nozzle is typically less than 100 nanometers.
The construction of such a shower head with numerous micro-nozzles is not elementary. Also, the showerhead is rather large and bulky. Still, a need exists in thrusters and in other applications for an electrospray source which produces multiple jets of a working fluid.